On June 12, 2009, the first case of novel influenza A H1N1(2009) virus infection was confirmed in Jiangsu Province. A virus with hemagglutination activity was isolated from the clinical samples derived from the patient using both MDCK cells and embryonic eggs, which was designated as A/Jiangsu/1/2009(H1N1). In order to monitor evolution of the virus, we carried out whole-genome sequencing, and analyzed the genetic characteristic of hemagglutinin (HA) of the isolate in detail. The results showed that HA did not contained the multibasic amino acid motif at cleavage sites, which is a characteristic of low pathogenic influenza viruses. Compared to reference virus A/California/04/2009, the HA protein of the isolate had four amino acid mutation, which were not located on the known antigenic sites. Consistent with the triple-reassortant swine H1 viruses from Northern America in recent years, the isolate contained five potential glycosylation sites, which also was the feature of classical swine H1N1 viruses. Compared with avian H1 viruses, two amino acid (E190D and G225D) were changed on receptor binding sites, which may be an important molecular mechanism of human-to-human transmission for the novel viruses. In this study, for the first time, we studied the molecular characteristics of the HA protein of the novel influenza A H1N1(2009) viruses in detail, which have an important guiding significance for further monitoring of virus mutation.
